diff --git a/addons/account/account.py b/addons/account/account.py
index c3cd13a8115..c37cc7dfb5e 100644
--- a/addons/account/account.py
+++ b/addons/account/account.py
@@ -1278,6 +1278,8 @@ class account_move(osv.osv):
         return super(account_move, self).copy(cr, uid, id, default, context)
 
     def unlink(self, cr, uid, ids, context=None, check=True):
+        if context is None:
+            context = {}
         toremove = []
         obj_move_line = self.pool.get('account.move.line')
         for move in self.browse(cr, uid, ids, context=context):